The present invention relates generally to adjustable-ride-position maintaining seat assemblies and more particularly to a simple seat assembly having a valve connected by a two-link linkage to the seat.
In the past, it was recognized that it would be desirable to have a vehicle seat which would absorb shocks and maintain a predetermined ride position across rough terrain regardless of the weight of the operator while featuring adjustment of the predetermined ride position to accommodate different size operators.
One of the first seats able to maintain an adjustable ride position is shown in the U.S. Pat. No. 3,210,019 granted to Elfes et al. on 16 Nov. 1965. The seat was made adjustable by having adjustment means for moving a platform relative to a base and placing a ride position maintaining device on the platform. The Elfes et al system was relatively complex in requiring separate means for adjustment and for maintaining the predetermined ride position.
Subsequently, a seat was developed such as that shown in the U.S. Pat. No. 3,638,897 granted to Harder, Jr., et al. on 1 Feb. 1972. The seat assembly moves substantially vetically by swinging on generally horizontal parallel linkages. To establish and adjust the ride position, a relatively complex three-link linkage is required to activate a valve which controls an actuator for raising and lowering the seat. To provide for large adjustments and to maintain the predetermined ride position, a specially fabricated flexible link is required between the seat and the valve.